Method for producing a foil material provided with an embossed hologram as well as a foil material

ABSTRACT

The invention relates to a method for producing a foil material, provided with an embossed hologram. Said method comprises the following steps: optionally metallizing said material, applying a lubricant and then directly embossing said material, the embossed surface remaining the material top layer. Said invention also relates to a foil material having the following structure: a metal layer, provided with an embossed hologram, and a lubricant layer, which is at least partially applied to said metal layer, whereby said material top layer is exclusively formed by the metal layer and/or the lubricant layer.

FIELD OF THE INVENTION

[0001] The invention relates to a method for producing a foil material provided with an embossed hologram, as well as such a foil material.

[0002] It is becoming more and more common in particular in the field of packaging technology to distinguish packagings by means of specific design features from competitive products so as to make it easier to recognise, in particular, imitations of trademark products. Holograms or holographic structures, for example, are hereby applied to the packaging material, in particular embossed therein, in order to make it possible to distinguish the packaging material and the product packaged therewith from other products.

PRIOR ART

[0003] Known from DE 37 44 650 A1 is a holographic embossing method, in which a substrate is provided with a lacquer layer, then metallisation of the material is carried out and finally a hologram is embossed through the metallisation. Lacquers having specific properties are required for such a method. Known for this purpose are lacquers which cure under UV light, said lacquers not being completely cured when embossing is carried out so that the embossing structure can be applied. The material is then normally provided with a protective lacquer and it can subsequently be cut into narrow rolls. It is alternatively known to carry out metallisation after embossing of the partially cured lacquer has taken place. The protective lacquer applied as the topmost layer is necessary to protect the fine embossing structures and to generate the required abrasion resistance and gliding property of the material. The known holographic embossing methods have the disadvantage that they always require an additional, separate production step during the manufacturing process. In particular, the embossing process has to occur before the covering protective lacquer is applied. The problem arises here that it is uneconomical to produce small lot sizes with varying embossed motifs since metallisation and coating with lacquer can only be carried out economically for large lot sizes, e.g. large rolls.

[0004] This disadvantage also applies to the production of a packaging material according to DE 299 00 043 U 1 and DE 299 04 872 U 1. The packaging material described therein also comprises a plastic layer as the outermost layer, which leads to the cited problems in view of economicalness.

DESCRIPTION OF THE INVENTION

[0005] The object of the invention is to create an economically improved method for producing a foil material provided with an embossed hologram, as well as a foil material which can be economically produced.

[0006] This object is solved by the method according to patent claim 1 and the foil material according to patent claim 5.

[0007] Within the scope of the method according to the invention, the foil material is first of all optionally metallised. It is noted at this point that the method according to the invention is basically suitable for metal foils, for example aluminium foils, for metal-paper composites, in particular aluminium-paper composites, and also for paper which is to be correspondingly metallised in a first method step, i.e. is to be provided with a thin metal layer. A lubricant is then applied within the scope of the method according to the invention.

[0008] Embossing of the metallised or metal layer occurs directly thereafter. In other words, the step normally required according to the prior art of applying a suitable lacquer in which the embossing structures are formed, is no longer required. Embossing is rather carried out directly on the metal layer. The lubricant hereby ensures that the required structures can be formed without the risk of the metal peeling off. Embossing essentially occurs directly on the finished foil material since embossing does not occur on a lacquer which still has to be subsequently cured, nor is a subsequently applied cover or protective lacquer required. It has shown during tests that with the exception of the lubricant layer, which is also present at least in residual amounts following embossing, the embossed surface can form the topmost layer of the foil material produced according to the invention.

[0009] Coating with a protective lacquer is no longer necessary. The method according to the invention thus achieves a noticeable economic improvement. As regards the foil material to be processed according to the invention, it is noted that this material can be material according to EP 0 676 503 A1, and the entire disclosure of this document concerning the material used according to the invention is herewith made the subject matter of the present application. Since the material mentioned therein already comprises a lubricant coating, it is obvious that a further lubricant coating is not absolutely necessary, but is, however, possible at any time.

[0010] A lubricant having a softening point which lies above the temperature occurring during embossing is preferably selected as the lubricant. Efficient production can hereby be ensured in an advantageous manner. In connection with the present invention, the usable lubricants preferably belong to the following chemical classes: paraffins, polyethylene waxes, polypropylene waxes modified with maleic anhydride, ester and acid waxes, amide waxes, polytetrafluoroethylene waxes, polytetrafluoroethylene/polyethylene waxes, ethyl vinyl acetate copolymer waxes, natural waxes, fatty alcohols, fatty acids, metal soaps, fatty acid esters, solid acid amides, siloxanes and sulphated oils. According to the invention, they can be used as individual compounds or in mutually compatible mixtures. Most lubricants are commercially available and can be used directly without any further preparation.

[0011] If the lubricant is a paraffin, it is preferably selected from predominantly branched-chain liquid hydrocarbons or from predominantly straight-chain solid hydrocarbons.

[0012] Polyethylene waxes as lubricants are preferably selected from polyethylenes having an average molecular weight of 2000 to 12000 or from air-oxidised, low molecular weight polyethylenes.

[0013] A preferred natural wax is carnauba wax.

[0014] Typical representatives of fatty acids as lubricants are stearic acid, 12-hydroxystearic acid and montan acids (mixture of long-chain carboxylic acids having 26 to 33 carbon atoms).

[0015] Metal soaps are also suitable as lubricants. Calcium stearate, magnesium stearate and zinc stearate are preferably used.

[0016] Fatty acid esters as lubricants are preferably selected from fatty acid esters of short-chain, monohydric alcohols, fatty acid esters of long-chain, monohydric alcohols, glycol fatty acid esters, glycerol fatty acid esters, montan acid ester waxes, solid or liquid high molecular weight mixed esters or esters of polybasic carboxylic acids.

[0017] Typical representatives of this class of compound are n-butyl stearate, stearyl stearate, propylene glycol monooleate, glycerol monooleate, glycerol monostearate, distearyl adipate, distearyl phthalate, polycondensates of pentaerythrite+adipic acid+oleic acid or stearic acid, and esters of montan acids mixed with free montan acids and calcium montanate.

[0018] A solid acid amide as the lubricant is advantageously a fatty acid amide selected from oleic acid amide, erucic acid amide or stearic acid amide, or N,N′-bis-stearoyl-ethylenediamine.

[0019] The lubricant is normally applied in that it is applied as a dispersion and then dried. The solvent used hereby evaporates so that a comparatively solid lubricant coating remains.

[0020] As regards the embossing of a hologram within the scope of the method according to the invention, it is noted that in contrast to another embossing wherein the entire material is deformed, only a deformation of the surface hereby occurs. In other words, the unprocessed “rear side” remains largely even when a hologram is embossed. A typical material thickness for the foil material used here is approximately 50 μm. A spacing of the embossing lines in the range of less than one micrometer, e.g. 0.5 μm, is also typical for the embossing of a hologram. Finally, it is preferred within the scope of the invention for embossing to be carried out in a continuous method, for example by rotation, i.e. by means of rotating rollers.

[0021] Preferred developments of the method according to the invention are described in claims 2 to 4.

[0022] Particularly good experiences have been had within the scope of the method according to the invention with paper which is firstly metallised. The method according to the invention can furthermore be applied in an advantageous manner to metal, in particular aluminium, foils or strips. Finally, a foil material having an embossed hologram, which consists of a metal-paper composite, in particular an aluminium-paper composite, can also be produced within the scope of the method. Such a composite material is to be coated with lubricant on the foil side, i.e. the metal side, within the scope of the method according to the invention, and can also be processed according to the invention without the need for a lacquer coating and can be made into a foil material having an embossed hologram.

[0023] It has proven to be advantageous for the application of the lubricant to apply the lubricant in an amount in the order of magnitude of 0.02 g/m². The required processability, in particular the possibility of embossing, can be hereby ensured in an economically favourable manner.

[0024] Since a subsequent application of a protective lacquer which possibly requires curing is not necessary according to the method of the invention, a cutting process is preferably carried out within the scope of the method according to the invention in a single operation together with embossing, which has further economic advantages. The material according to the invention can, in particular, be produced on a combined embossing and cutting machine, in particular a roll cutting machine. The material can then be wound with little effort to at least one roll.

[0025] The aforementioned object is furthermore solved by the foil material described in claim 5. Said foil material comprises a metal layer provided with an embossed hologram as well as a lubricant layer which is applied to the finished foil material at least partially on said metal layer. The method according to the invention is reflected in the associated foil material in that the topmost layer of the material is exclusively formed by the metal layer and/or the lubricant layer. In other words, according to the invention, no protective lacquer is needed on the foil material. A material which can be produced in an extremely economical manner is thus created, which can, for example, be used as an inner foil for cigarette packets.

[0026] Preferred embodiments of the foil material according to the invention can be found in the subsequent claims. Essentially in accordance with the embodiments of the method according to the invention, it is preferred for the foil material to be a metallised paper, a metal foil, in particular an aluminium foil, or a metal-paper composite, in particular an aluminium-paper composite.

[0027] The required processability for producing the foil material according to the invention can be ensured in that the finished material has a lubricant coating in the order of magnitude of 0.02 g/m².

[0028] It is finally preferred from the point of view of economics and transport for the foil material according to the invention to be a roll of material. 

1. Method for producing a foil material provided with an embossed hologram and having a metal layer, comprising the following steps: applying a lubricant, and directly thereafter embossing the material, the embossed surface remaining the topmost layer of the material.
 2. Method according to claim 1, wherein the material is an aluminium foil, an aluminium-paper composite or metallized paper.
 3. Method according to claim 1 wherein the lubricant is applied in an order of magnitude of 0.02 g/m².
 4. Method according to claim 1, wherein a cutting process occurs in a single operation together with embossing, which is followed by winding onto at least one roll.
 5. Foil material comprising a metal layer having an embossed hologram therein, a lubricant layer which is at least partially applied to said metal layer, wherein the topmost layer of the material is formed exclusively by the metal layer and/or the lubricant layer.
 6. Foil material according to claim 5, wherein the material is a metallized paper, an aluminium foil or an aluminium-paper composite.
 7. Foil material according to claim 5 wherein the material has a lubricant layer in an order of magnitude of 0.02 g/m².
 8. Foil material according to claim 5, wherein the material is a roll of material. 